I've been able to get most of Coltrane's Impulse albums without really trying. I think non-jazz people buy them, get scared when things go all altissimo and sell them again. Ditto Archie Shepp, I've managed to pick up almost every Impulse album used in the past year. I remember when Ahmad Jamal albums were everywhere, but nowadays they get bought quickly. I work near two used record stores and I could pretty much buy Bob James entire non-ESP output in the next 15 minutes if needed.